-LRB- CNN -RRB- -- As Congress prepares to return from its August recess , Washington is gearing up for a national conversation on the balance between security and liberty , between necessary surveillance and necessary privacy .

That 's a good thing .

It would be an even better thing if the discussion were based on fact rather than contaminated by inaccuracies and posturing . A quick review of recent commentary suggests that may not be likely .

For example , Fox News seems incapable of commenting on this story without the header `` NSA Scandal , '' a lead that brings with it its own conclusion .

A prominent U.S. senator recently opined that , `` They -LRB- the National Security Agency -RRB- basically I believe probably are looking at all the cell phone calls in America every day . ''

Another lawmaker has already concluded that the NSA is `` an agency out of control . ''

And a former congressman on a Sunday talk show added to the sum total of human knowledge with this : `` CIA ! Hello ! I mean we have a CIA . What 's the NSA really about ? ''

I fear that the coming debate will have all the characteristics of a mob -- thoughtless action driven by artificial urgency , unreasoning fear , emotion and misinformation .

And that 's a pity since the heart of this issue has been around for years and deserves serious discussion .

As far back as at least 2000 , the NSA tried to hit the real question head-on . The agency knew that past targets of its surveillance largely communicated on their own dedicated networks . There was hardly a civil libertarian alive who would be concerned about trying to intercept communications between the Soviet high command in Moscow and intercontinental ballistic missile silos beyond the Urals .

But the threats of the 21st century do not communicate on their own networks . Terrorists , drug traffickers , arms proliferators and the like live on a unitary global information grid where their communications co-exist with the communications of the very people the NSA is committed to protecting .

It was clear even pre-9 / 11 that the NSA could not do its mission without working aggressively on this common grid . It was also clear that the agency would not have the power to do so -- legally , financially or technologically -- unless the American people were convinced that this power would be limited to its intended purpose , that even as constitutionally protected communications mingled with and were sorted from targeted communications , they would still be protected .

And that basically is the issue of the moment , whether the headline is PRISM , XKeyscore , metadata , `` upstream '' communications , Blarney or an alleged NSA secret room at an AT&T facility in San Francisco -- all of which have been featured in recent coverage .

Americans will have to decide what constitutes a `` reasonable '' expectation of privacy and what running room they will give their government to search for the signals almost everyone agrees should be captured even as those signals co-exist with their own .

Although Congress , the courts and two administrations have authorized what the NSA is doing today , these are not easy issues . Resolution will hinge on how much trust people have in their government , or at least this part of it . It will also hinge on how much danger with which people are willing to live .

And if this is to be a fact-based discussion , resolution will also hinge on how well citizens understand a few basics of what exactly is being done . Unfortunately , much of the public discourse is confused to the point of incoherence .

Take the question of authorities . How does the NSA get the power to do any of this ? In most instances , since this is about foreign intelligence , authority comes from the president and is codified in Executive Order 12333 .

Only when a U.S. person is involved or for certain kinds of collection in the United States does the agency have to rely on the Foreign Intelligence Surveillance Act and the court it established .

This is important . Most intelligence collection -- by the NSA , CIA or any intelligence agency -- is not overseen by a court . Oversight comes from the president and the Congress . But it is still oversight . Breathless claims that some things are done without court review could well be true -- and not very relevant .

Then there is collection involving Americans . Most casual commentators simply assert that anytime the NSA is listening to an American , the agency must have a warrant . Indeed , trying to calm current concerns , President Barack Obama told Charlie Rose that , absent a warrant , `` What I can say unequivocally is that if you are a U.S. person , the NSA can not listen to your telephone calls . ... ''

Actually , that 's not quite correct -- and never has been . As the president suggested later in the interview , the NSA can not target the communications of a U.S. person . If it is tracking the communications of a legitimate foreign intelligence target and that target talks to an American , the NSA indeed covers it -- and always has .

This simply makes sense . Picture a known terrorist who makes a series of operational calls to confederates in say Paris , London and the Bronx . To suggest that the NSA has to stop coverage of the last call is ludicrous .

This is what the NSA calls incidental collection of information to , from or about a U.S. person . When this occurs -- and it is not rare -- the agency is required to keep its focus on the foreign intelligence in the communication and minimize or mask the U.S. identity unless the identity is essential to the intelligence -LRB- as it would be in the example above -RRB- .

Keep this in mind when commentators claim that the NSA has collected the content of American e-mails or phone calls . That may be , but the NSA is not targeting them without a warrant .

And then there are the numbers . Like The Washington Post 's August 15 headline screaming , `` NSA broke privacy rules thousands of times per year , audit finds . ''

You have to dig deeper to learn -LRB- as I pointed out in another piece -RRB- that all of the incidents were inadvertent ; no one is claiming that any rules were intentionally violated ; and all of the incidents were discovered , reported and corrected by the NSA itself .

In one example , the Post referred to `` large numbers of data base query incidents . '' The NSA later confirmed that in one quarter there indeed were 115 incidents of NSA queries being incorrectly entered , mistakes such as mistyping or using overly broad search criteria . That 's 115 out of more than 61 million inquiries made in that quarter , a compliance rate of .999998 .

In this , as in most issues , facts -LRB- and context -RRB- matter .

Understanding beyond the accusatory headline or the facile quip is needed , or we will be just tossing slogans at one another , slinging volleys of hyperbole , stoking fears and anger and distrust , all of which will make it even more difficult to resolve an already very difficult question .

The opinions expressed in this commentary are solely those of Michael Hayden .

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Michael Hayden : It 's good for U.S. to discuss balance between liberty and security

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Former NSA director says much has been misunderstood in recent debate on agency

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He says Americans are only surveilled when in contact with foreign agents

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Hayden : Violations of rules were discovered by NSA , represent tiny fraction of communications